1. Field of the Invention
The present invention relates to a thin film device having a thin film coil wound on a magnetic film.
2. Background Art
Recently, a thin film device having a thin film coil is widely used in a field of electronic instruments for various applications. As an example of the thin film device, a thin film inductor being an inductive circuit element is given.
As a type of the thin film coil mounted in the thin film device, a spiral type is used in accordance with requirement of size reduction (reduction in device area) and low profile (reduction in device thickness), however, a solenoid type is used in an application in which performance is required to be improved in addition to size reduction and low profile (for example, refer to Japanese Unexamined Patent Publication No. 05-029146). In the thin film device having the thin film coil of the solenoid type, an excitation conductor is arranged around a thin film magnetic material (magnetic core) in a solenoid shape, so that inductance can be increased compared with a case that the thin film coil of the spiral type is provided.
As the thin film coil of the solenoid type, a thin film coil having a coil structure being divided into a plurality of parts is known (for example, refer to Japanese Unexamined Patent Publication No. 2004-296816). The thin film coil includes first and second coil conductors formed on one surface and the other surface of a magnetic insulating substrate respectively, and connection conductors formed in through-holes penetrating through the magnetic insulating substrate, the coil conductors and the connection conductors being connected to each other. Thickness of the first coil conductor and thickness of the second coil conductor are the same to make DC resistance uniform over the whole thin film coil.